Persistent neck pain of greater than six months duration is a frequent occurrence in both men and women and patients with neck pain are the second biggest group (after patients with low back pain) attending physical therapy and chiropractic clinics for relief of their symptoms. Further, research shows that about one third of patients diagnosed with whiplash associated disorders, (a variety of clinical manifestations due to bony or soft tissue neck injuries following an acceleration-deceleration energy transfer sustained from a motor vehicle accident), only gain short-term relief by conventional musculoskeletal approaches, which by definition are an ineffective treatment. Preventing a portion of patients with neck pain to enter the chronic phase of their condition imposes a great challenge for clinicians.
Non-invasive methods have been developed to quantify abnormal motions of the cervical spine segments using biomechanical parameters. Patent application W0 91/15148 discloses a method that uses instantaneous axis of rotation (IAR) of normal and abnormal Range of Motion. Measurement of the IAR detects kinematic joint function but not sensorimotor function. The same applies to the method disclosed in U.S. Pat. No. 5,954,674, where each patient is trained to move his/her head in a predetermined manner in predetermined planes of motion at a predetermined velocity. While the patient moves the joint in the aforementioned predetermined single plane of motion, biomechanical data is gathered pertaining to the instantaneous helical axis of rotation of the cervical spine segments.
Patent application W0 2004/043257 describes a device for the diagnosis and/or therapy of functional disorders of the cervical spine. The patient is required to follow an optical signal with the head by a tracking system which moves along a predetermined horizontal or vertical line/path at a predetermined speed in a recurring way. The path is usually a straight line but with a specific vertical or horizontal displacement/deflection or amplitude. To make the movement path easier or more difficult the length of the movement line can be shortened or made longer and the speed at which the optical signals moves for a given path can be reduced or increased. W0 2004/043257 uses electromyography (EMG) signals from the muscles, especially m. semispinalis capitis, as an outcome measure.
The observed individuality in sensorimotor disturbances in patients with neck pain suggests that it may be important to develop specific rehabilitation programs for specific dysfunctions and to use objective and quantitative methods for evaluation of the effects of rehabilitation. The term “sensorimotor” incorporates all the afferent, efferent, and central integration and processing components involved in maintaining stability in the postural control system through intrinsic motor control properties. From a clinical orthopaedic perspective, the peripheral mechanoreceptors are the most important in functional (muscular-neural) joint stability but in the cervical region they are also important for postural stability, head-neck and eye movement control.
Consequently, conventional musculoskeletal approaches may be sufficient only for patients with neck pain and minimal sensorimotor disturbances. Clinical experience and research indicates that in cases of significant sensorimotor disturbances, this might be an important factor in the maintenance, recurrence, or progression of various symptoms in patients with neck pain. In these cases more specific and novel treatment methods are needed which progressively address neck position and movement sense as well as cervicogenic oculomotor disturbances, postural stability, and cervicogenic dizziness.
Since they were introduced in 1906 by Slinger and Horsley (Slinger (1906)), simple target-matching tasks have been widely used clinically to measure accuracy of movement. The neuromuscular mechanism controlling the head on the body has been tested either by relocation of the natural head posture (NHP) (Revel (1991), Heikkilä (1996), Rix (2001)) or relocation of a set point in range. (Loudon (1997)) These traditional cervicocephalic kinesthetic tests are limited because they measure only one aspect of proprioceptive function: position sense. An important function of the proprioceptive system in neuromuscular control is to correct movement on a moment-to-moment basis. This is especially the case when non-learned complex movements are performed.
In a prior study (Kristjansson (2001)) subjects were required to trace a discreet figure of 8—movement by repeated movements of their head. Each time a cross-over in the figure of 8 was made, the subjects were asked to move their nose through the starting natural head posture (NHP) as accurately as possible. This test was too difficult for both asymptomatic and symptomatic subjects to be clinically useful.
A “laser beam method” has been used by some therapists to track predetermined patterns such as a figure of eight, ellipsoids, polygons and the like, placed in front of the patient (See patent application WO 01/76478). The motion patterns in the laser beam method are highly predictable and therefore do not challenge the proprioceptive system, which needs unpredictable movement patterns of incremental difficulty for accurate assessment and to enhance treatment progression. Furthermore, the outcome measures in the laser beam method are not readily available for clinical judgment of the patient's ability to trace the pattern accurately and smoothly and the most important variables (amplitude accuracy, directional accuracy and jerk index), are not used (as in the present invention) to monitor the status of each patient's sensorimotor movement control for objective assessment and to enhance graded progression in the treatment of said sensorimotor impairment.
Inventor's previously introduced clinical method measures the patient's ability to correct cervical spine movements on a moment-to moment basis, which is an important proprioceptive function for the regulation of movements, i.e. detection and correction of errors, when performing active movements, via feedback and reflex mechanisms. This method and system, called “the Fly” demonstrated impaired movement patterns in patients with a whiplash injury when compared to controls. (Kristjansson (2004)).
Different theories about motor control such as reflex, hierarchical and system theories underpin the design of this prior test. (Shumway (2001)). These theories suggest that the test movement needs to be slow, unpredictable and of short duration in order to challenge deficits in the cumulative input from the mechanoreceptors which give rise to neck proprioception. The slow speed ensures that over-stimulation of the neck mechanoreceptors and of the specialised mechanoreceptors in the vestibular system is avoided. A slow speed is also necessary for the subjects to be able to rely on feedback from the neck mechanoreceptors during movement. The movement path must be unpredictable and of short duration to avoid programming and learning effects. In addition, the system theories tell us that because the final goal of a movement takes priority over everything else during task performance, movement paths for the same task may differ each time the task is repeated. An unpredictable test path is therefore preferred.
In “the Fly” (Kristjansson (2004)), the patient sits in front of a computer with one or more sensor mounted on the head, which accurately measures the positions and movements of the head-neck in space. Two cursors are visible on the computer screen: one black indicating the movements of the head-neck sensor and the other blue, the target cursor derived from “the Fly” software program, which target cursor traces the path to be followed. At the very beginning of the test both cursors match each other in the middle of the screen. Then the blue target cursor starts to move. The patient is instructed to follow “the Fly” cursor, tracing slow movement patterns of short duration, with the black cursor, by moving the head-neck and thus the mounted sensor, as accurately as possible. The deviation or amplitude accuracy between the two cursors is continuously recorded during three randomly ordered test sequences.
It would however be appreciated to be able to more precisely grade the impairment level of an individual patient and use such a motion tracking method and system as a treatment method, starting at each individual's respective impairment level and going through progressively more difficult levels of training.